The invention pertains to a combustible propellant charge casing for ammunition which can be shot from the barrel of a weapon.
High-energy propellant powder such as that required for shooting performance-enhanced projectiles produces high temperatures and pressures in the weapon barrel in question and thus also leads to increased wear of the barrel through erosion. To reduce this type of erosion, it is known that talc, wax, or a similar material can be mixed into the propellant powder. It has been found, however, that the erosion-reducing effect of such additives is relatively weak.
From DE 39 27 400 A1, furthermore, it is known that wax or paraffin as erosion-reducing material can be mixed not with the propellant powder but rather with the molded part of the ammunition consisting of a combustible plastic shrink film. A significant reduction in the erosive action of the propellant gases on the inside wall of the weapon barrel in question has not been achieved in this case either.
It is known from U.S. Pat. No. 3,403,625 and U.S. Pat. No. 3,426,684 that WO3 or MoO3 can be added as erosion-reducing additives to the propellant powder. When the cartridges in question are fired, a protective layer which has the effect of reducing the erosive action of the propellant gases is said to form on the inside wall of the weapon barrel. It is also mentioned in these publications that, in the case of cartridges with combustible propellant casings, the erosion-reducing additives can also be introduced into the propellant casing. Detailed information on the specific composition of the substances to be introduced into the propellant casing, however, cannot be extracted from these publications.
Finally, a combustible propellant charge casing is disclosed in DE 101 03 912 A1 filed by the applicant, in which an oxide of one of the rare earth elements, especially La2O3, CeO2, or Y2O3 or one of the elements of the 6th subgroup of the periodic system, especially MoO3 or WO3, or polyoxymethylene (POM), or a combination of these substances is used as an erosion-reducing substance. The amount of erosion-reducing additive in the propellant casing should be in the range of 2-15 wt. %.
As the applicant has discovered, the surprisingly good erosion-reducing action of the oxides introduced into the propellant charge casing is not attributable to, for example, the formation of a protective layer on the inside wall of the weapon barrel but rather on the reduction of the atomic hydrogen molecules produced during the combustion of the propellant powder (atomic hydrogen attacks the grain boundaries of the chromium layer and of the steel, loosens the microstructure, and leads to the break-out of individual grains and thus to erosion). The atomic hydrogen which forms at high temperatures releases energy (432 kJ/mole) as it forms hydrogen molecules, and this reaction normally contributes significantly to the heating of the inside wall of the barrel (2(H)→H2+432 kJ). With the trioxides of tungsten and molybdenum, however, hydrogen reacts exothermically at temperatures above 800° C. and 1,000° C., respectively, as follows:WO3+6<H>→W+3H2O+14 kJ (at 800° C.)MoO3+6<H>→Mo+3H2O+14 kJ (at 1,000° C.).
Finely distributed WO3 or MoO3 in the combustible casing reaches temperatures of more than 1,000° C. when the powder burns and thus reacts completely with both atomic and molecular hydrogen.
In the reaction of atomic hydrogen, the enthalpy of the formation of molecular hydrogen is 432 kJ/mole. After subtraction of the exothermic enthalpy of the reduction of WO3, an enthalpy reduction of about 426 kJ/mole is obtained, where one mole of WO3 reduces 3 moles of H2.
When MoO3 is used, the enthalpy is reduced by about 395 kJ/mole. As a result of the reduction of the oxidizing agents WO3 and/or MoO3, some of the atomic hydrogen formed during combustion of the powder is consumed and thus cools the gas formed by the powder on the inside barrel wall and the inside barrel wall itself. The resulting additional water vapor from the reaction of WO3 and/or MoO3 produces a cooling pipe flow along the inside wall of the barrel.
Additional reaction partners for hydrogen are the oxides of bismuth, manganese, and yttrium and especially La2O3 and CeO2 as well as organic compounds which easily break down into small radicals and trap the atomic hydrogen immediately. Thus, energy is consumed when polyoxymethylene (POM) decomposes into CH2—O radicals.